Filtering
Every inbound message passes through our filtering servers before it reaches your mail server.
- Spam filtering for unwanted bulk and unsolicited mail.
- Virus and malware filtering for infected attachments and malicious content.
- Phishing and spoofing protection for messages that impersonate people or brands.
- Geographic filters to treat mail from chosen countries differently.
- Attachment-type filters to block file types your business never needs.
- Microsoft Office macro filter for documents that carry macros.
- Custom domain rules in advanced settings, for cases the defaults don't cover.
No filter is perfect. Some spam will get through, and occasionally a legitimate message will be held. The quarantine and lists below are how you deal with both.
Feature guide
| Feature | What it does | Learn more |
|---|---|---|
| Quarantine and digests | Personal quarantine for every user, scheduled digest emails, shared admin quarantine | Quarantine and digests |
| Allow and block lists | Approve or block senders, with sender verification against spoofing | Allow and block lists |
| Outage spooling | Holds mail for up to 5 days if your mail server is down | Outage spooling |
| Outbound relay | Smart host with DKIM signing and outbound filtering, 500 messages a month | Outbound relay |
| Domain monitoring | Alerts when your MX, SPF or DMARC records change | Domain monitoring |
| DMARC monitoring | Collects your DMARC reports, shows who sends as your domain and when to tighten your policy | DMARC monitoring |
| Lookalike Domain Watch | Daily checks for look-alike domains, with alerts when one is registered or gets a mail server | Lookalike Domain Watch |
Visibility
Message history
Message history is kept for 30 days. When someone says "I never got that email", you can search for it and see what happened to it, such as whether it was delivered or quarantined.
Monthly owner report (Protect Plus)
A plain-English summary for the business owner each month, so you can see the service working without logging in.
Mail stats in your portal
Your portal shows messages delivered and held, what's waiting in quarantine, and a 30-day trend for each domain, updated daily.
Lookalike domain alerts
Every day we check names that look like your domain: typos, swapped or doubled letters, look-alike characters and other endings such as .net or .co. When one is registered, or starts accepting email, we email you with what to do. It detects look-alikes; it can't take them down. See Lookalike Domain Watch and lookalike domain phishing.
Account security
Customer accounts support two-factor sign-in with an authenticator app, and owners can require it for everyone. An activity log shows sign-ins, failed attempts and changes to domains, billing and security settings, and we email you when your password, sign-in email or two-factor settings change.
Setup and safety
Guided setup wizard
The wizard shows your current DNS next to the new values, walks through platform-specific steps and saves rollback instructions. It supports:
- Microsoft 365, with an inbound Partner connector and Enhanced Filtering for Connectors
- Google Workspace, with an inbound gateway
- cPanel/WHM
- Exchange and other standards-based mail servers
Protect Plus also includes a human setup session with our team.
Free Check tools
All of our tools are free and need no account: Email Health Check, MX Lookup, SPF Checker, DMARC Checker, DKIM Checker, Email Header Analyzer, Blacklist Checker, Reverse DNS (PTR) Lookup, MTA-STS Checker, BIMI Checker, SPF Record Generator, DMARC Record Generator, SMTP Error Code Lookup, Email Deliverability Test, DMARC Report Analyzer and DKIM Key Generator, plus SPF records by email provider. The header analyzer, the DMARC Report Analyzer and the DKIM Key Generator run in your browser and upload nothing.
Limits, stated plainly
Every domain, on both plans, includes:
| Limit | Included per domain |
|---|---|
| Mailboxes | Unlimited (mailbox count, not message volume) |
| Domain aliases | Unlimited |
| Inbound messages | 100,000 per month |
| Maximum inbound message size | 400 MB |
| Outbound relay messages | 500 per month |
| Outage spooling | Up to 5 days |
| Message history | 30 days |
Plan comparison
| Item | Protect | Protect Plus |
|---|---|---|
| All filtering and quarantine features | Yes | Yes |
| Outbound relay (500/month) | Yes | Yes |
| Domain monitoring | Weekly | Daily |
| Monthly owner report | No | Yes |
| Human setup session | No | Yes |
DMARC monitoring
Point your DMARC reports at us (rua=mailto:dmarc@iblockspam.com) and your portal shows who sends mail as your domain, whether each sender passes SPF, DKIM and DMARC, which senders need fixing and what looks like spoofing. When your own senders pass consistently, it tells you when it's safe to move from p=none to quarantine, then reject. Report counts come only from receivers that send reports. More on the DMARC monitoring page, or read how to read DMARC reports.
Click through all of this with sample data in the portal demo. Not ready to switch? Free Domain Watch checks one domain's public records every week at no cost.
See pricing for current beta prices, why businesses choose iBlockSpam, or the FAQ for common questions.
Frequently asked questions
Which features differ between Protect and Protect Plus?
Filtering, quarantines, outage protection, message history and outbound relay are the same on both plans. Protect Plus adds daily domain monitoring instead of weekly, a monthly owner report and a human setup session. Pricing is per domain on both plans.
Is there a limit on mailboxes?
No. Each domain includes unlimited mailboxes and unlimited domain aliases, so you don't pay per user. Message volume is limited: 100,000 inbound messages per domain per month, with a 400 MB maximum inbound message size.
Do you offer DMARC reporting?
Yes. DMARC monitoring is included in Protect and Protect Plus: add our report address to your DMARC record and your portal shows who sends mail as your domain, what passes, what needs fixing and when it's safe to move to a stricter policy. Counts come only from receivers that send reports.
Related guides
How do spam filters work?
How inbound spam filters decide what reaches your inbox: connection checks, reputation, SPF/DKIM/DMARC, content rules, attachment scans and quarantine.
9 min read Email security basicsWhat is an email quarantine, and how should you use it?
What an email quarantine is, personal vs admin quarantine, digest emails, retention limits, and how to release messages without letting phishing back in.
8 min read Phishing & threatsWhich email attachment types are dangerous, and what should you block?
Which email attachment types are dangerous, from .exe and scripts to macros, HTML, SVG, ISO and OneNote files, and which to block outright versus quarantine.
9 min readLast updated: